Lasse Daniel Efskind (born 13 February 1944) is a Norwegian medical doctor, primarily known for his speedskating career and his books.
For several years he skated at close to national top level, concurrently with political activism and his education in civil engineering and medicine.
Efskind's The Soldier's Little Red Book was published in 1970 and caused public sphere as well as legal controversy, as it was concerned with political organisation within the armed forces.
Later books with fellow speedskater and medical doctor Asle T. Johansen have been of the "exotic group bicycling excursions" type, with emphasis also on the philosophy of travelling.
These excursions have included bicycling around the Earth in 80 days; the route of Mao's Long March; on the roof of the world in Tibet; and via the Andes to the source of Amazon River.